Frequency compensator



TUNED T0 RESONATE AT NORMAL FREQUENCY.

M. A. EDWARDS ET AL FREQUENCY COMPENSATOR Filed May 27, 1939 SATURATED EXCITATION CONTROLLING MEANS March 19, 1940.

Inventors: Martin Afidwards, Richard W. Port r" by W. 0) 44/1 Their Attorney.

Patented Mar. 19, 1940 UNITED STATES PATENT OFFICE- FREQUENCY OOMPENSATOR Martin A. Edwards and Richard W. Porter,

Schenectady, N. Y., assignors to General Electrio Company, a corporation of New York Application May 27, 1939, Serial No. 276,211

4 Claims. (01. 171-119) This invention relates to frequency compenwindings 4 and 5 which are energized in accordsators and more particularly to an arrangement ance with the voltage of the alternator by means for compensating the electro-responsive primary of an adjustable auto-transformer- 6 for adjustcontrol circuit of a regulator of an alternating ing the level of the voltage held by the regu- 5 quantity whose frequency is subject to departures lator system. Rectifiers l and 8 are provided 5 from a normal value for errors produced by said for causing direct current to flow in each of the departures. windings. A normally highly saturated reactor Many circuits which measure an alternating 9 is connected inthe input circuit of the rectifier quantity, such for example as the voltage of an 8. This circuit may be considered the primary in alternating current circuit, are reactive in charcontrol circuit of the regulator. 1o acter so that if the frequency of the measured At normal voltage the winding 4 predominates quantity is variable the accompanying changes slightly over the winding 5 so that a net or rein the reactance of the measuring circuit produce sultant magnetizing effect of the two windings errors in the response. causes the excitation controlling means to pro- In accordance with our invention these errors vide suflicient' excitation to maintain normal 15 are corrected or compensated for by the comvoltage. If the voltage increases the current bination of a resonant circuit and a reactance. in the winding 5 increases by a greater per- The resonant circuit is tuned to resonance at centage than the current in the winding 4 due the normal frequency of the measured alternatto the saturated condition of the reactor 9. This so ing quantity so that departures from the normal increases the net or resultant ampere turns of the frequency produce dissonance. The current actwo coils and causes the excitation controlling companying this condition of dissonance will be means to reduce the excitationand consequently leading or lagging depending upon the direction the voltage of the main machine. Conversely, in which the frequency has departed from norupon a decrease in regulated voltage the current mal. This reversible phase current when passed in the primary winding 5 decreases by a greater g5 through the reactance produces a reversible voltpercentage than the current in the winding 4, age which is applied to the measuring circuit thereby decreasing the, net ampere turns of the so as to compensate it for its change in retwo control windings and causing an increase in actance and thus compensate the measuring cirthe excitation and voltage of the main machine.

cuit for frequency errors. windings 4 and 5 may be field windings on 30 An object of the invention is to provide a an exciter or they may be operating windings new and improved frequency compensator circuit. on the solenoid core of a regulator for the ex- Another object of the invention is to provide a citation of an exciter. novel and simple system for compensating a cir- If the speed of alternator I changes. its frecuit which measures an alternating quantity for quency changes and as the reactanceof reactor 35 errors produced by variations in the frequency 9 is sensitive to variations in frequency the curof said quantity. rent in the control winding 5 will vary with varia- Another object of the invention is to provide a tions in frequency and thus will cause a frenovel and simple frequency compensator for alquency error.

ternating current voltage regulators. This is compensated for by energizing the 40 The invention will be .better understood from winding 5 from across a parallel resonant cirthe following description taken in connection cuit comprising a capacitor l0 and a reactor H. with the accompanying drawing and its scope will This parallel resonant circuit is connected in be pointed out in the appended claims. series with a second reactor l2 across the output Referring now to the single figure of the acterminals of the transformer 6, that is to say, it is 45 companying drawing, which illustrates diagramconnected in parallel with the input terminals matically an embodiment of our invention, we of the rectifier I supplying the control winding 4. have shown therein an automatic voltage regula- The resonant circuit is tuned to resonate at tor system for a three-phase synchronous dynamo the normal frequency of the alternator l. Conelectric machine I having a field winding 2. The sequently, at normal frequency substantially no 50 excitation of the field winding is controlled by current flows through the parallel resonant cirany suitable excitation controlling means 3, such cuit and its impedance is substantially infinite. for example as a direct current exciter or counter Therefore, substantially all of the voltage ap- E. M. F. machine. The excitation controlling plied to the series circuit containing the resonant 5 means is controlled by a pair of opposed control circuit and the reactor 12 appears across the resonant circuit so that the voltage applied to the input terminals of the rectiflers I and 8 is the same.

If now the frequency decreases the reactanceof the capacitor I0 increases and the reactance of the reactor I I decreases. This causes a lagging current to be drawn through the reactor I2, thus producing a voltage drop, that is to say, a voltage which subtracts from the voltage applied to the 10 parallel resonant circuit and consequently subtracts from the voltage which is applied to the primary control circuit. As the effect of the decrease in frequency is also to decrease the reactance of reactor 9 and consequently to increase the current in the winding 5, the effect of the voltage drop produced in the reactor l2 tends to offset the change in the reactance of the reactor 9, and by properly proportioning the elements substantially exact compensation can be secured for a reasonable decrease in frequency. In this manner the current in the-winding 5 will be substantially independent of decreases in frequency. In a similar manner if the frequency increases the reactance of capacitor l0 decreases and the reactance of reactor H increases, thus causing a leading current to flow through the reactor I2. This leading current in the reactor causes a voltage rise or increase to be applied to the primary control circuit which compensates this circuit for the decrease in current caused by the normal increase in reactance of the reactor 9 with increases in frequency.

It will thus be seen that the reversible phase current produced by dissonance in the parallel ,resonant circuit causes a reversible voltage to be produced inthe reactor l 2 which substantially exactly compensates the primary control circuit for the changes in impedance of the reactor 9 with changes in frequency. v While the invention has been described inconnection with a regulator control circuit having two windings, it will of course be-obvious to those skilled in the art that it may also be applied to control circuits or measuring circuits,

generally having any number of windings.

While there has been shown and described a particular embodiment of this invention, it will be obvious to those skilled in theart that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of, the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A frequency compensator for an automatic alternating voltageregulator of the type having a relatively highly inductive primary control circuit comprising, in combination, a pair of serially connected reactors connected to respond to the regulated alternating voltage, a capacitor, said control circuit and said capacitor being connected across one of said reactors, said capacitor and the reactor it is connected across being so proportioned as to resonate at a predetermined normal frequency of said regulated alternating voltage, the other reactor being so proportioned that the variations in voltage across it caused by a dissonance current flow through said normally resonant capacitor and reactor when the frequency of the regulatedvoltage departs from normal substantially compensates said control circuit for the effect of. changes in its inductive reactance resulting from said frequency departures from normal, whereby said primary voltage responsive control circuit is substantially independent of reasonable frequency variations.

2. In a regulator system for the magnitude of an alternating electrical quantity whose frecuit that the changes in voltage across it with changes in frequency caused by a dissonance current through said resonant circuit when the frequency departs from normal substantially compensates said control circuit for the changes in'its impedance caused by said frequency departures. I

3. A frequency compensated electro-responsive system responsive to the magnitude of anelectrical quantity comprising, in combination, a reactive primary electro-responsive circuit connected to be energized in accordance with the value of said Quantity, the, reactance of said circuit causing an error in the action of said system when said frequency departs from normal, a

resonant circuit connected to respond to the frequency of said quantity and proportioned to resonate at said normal frequency, and means 1 responsive to a dissonance condition of said resonant. circuit when said frequency departs from normal for applying a compensating quantity to said control circuit so as to correct said error.

4. In a regulator system for an alternating voltage whose frequency varies from a normal value comprising, in combination, apparatus for controlling the magnitude of said voltage, a pair of opposed control coils for controlling said apparatus, one of said control coils being energized in direct proportion to said voltage, a parallel resonant circuit, a reactor, said resonant circuit and said reactor being connected in series with each other so as to be energized in accordance with the magnitude of said voltage, the other control coil being connected across said parallel resonant circuit, and a normally sat-- .urated reactor connected in series with said last mentioned control coil, said resonant circuit of said voltage. a

- MARTIN A. EDWARDS.-

RICHARD W. PORTER.

' being tuned to resonate at the normal frequency 

